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  <div class="section" id="buffer-protocol">
<span id="bufferobjects"></span><span id="index-0"></span><h1>缓冲协议<a class="headerlink" href="#buffer-protocol" title="永久链接至标题">¶</a></h1>
<p>在 Python 中可使用一些对象来包装对底层内存数组或称 <em>缓冲</em> 的访问。此类对象包括内置的 <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> 和 <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> 以及一些如 <a class="reference internal" href="../library/array.html#array.array" title="array.array"><code class="xref py py-class docutils literal notranslate"><span class="pre">array.array</span></code></a> 这样的扩展类型。第三方库也可能会为了特殊的目的而定义它们自己的类型，例如用于图像处理和数值分析等。</p>
<p>虽然这些类型中的每一种都有自己的语义，但它们具有由可能较大的内存缓冲区支持的共同特征。 在某些情况下，希望直接访问该缓冲区而无需中间复制。</p>
<p>Python 以 <a class="reference internal" href="#bufferobjects"><span class="std std-ref">缓冲协议</span></a> 的形式在 C 层级上提供这样的功能。 此协议包括两个方面:</p>
<ul class="simple" id="index-1">
<li><p>在生产者这一方面，该类型的协议可以导出一个“缓冲区接口”，允许公开它的底层缓冲区信息。该接口的描述信息在 <a class="reference internal" href="typeobj.html#buffer-structs"><span class="std std-ref">Buffer Object Structures</span></a> 一节中；</p></li>
<li><p>在消费者一侧，有几种方法可用于获得指向对象的原始底层数据的指针（例如一个方法的形参）。</p></li>
</ul>
<p>一些简单的对象例如 <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> 和 <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> 会以面向字节的形式公开它们的底层缓冲区。 也可能会用其他形式；例如 <a class="reference internal" href="../library/array.html#array.array" title="array.array"><code class="xref py py-class docutils literal notranslate"><span class="pre">array.array</span></code></a> 所公开的元素可以是多字节值。</p>
<p>缓冲区接口的消费者的一个例子是文件对象的 <a class="reference internal" href="../library/io.html#io.BufferedIOBase.write" title="io.BufferedIOBase.write"><code class="xref py py-meth docutils literal notranslate"><span class="pre">write()</span></code></a> 方法：任何可以输出为一系列字节流的对象可以被写入文件。然而 <code class="xref py py-meth docutils literal notranslate"><span class="pre">write()</span></code> 方法只需要对于传入对象的只读权限，其他的方法，如 <a class="reference internal" href="../library/io.html#io.BufferedIOBase.readinto" title="io.BufferedIOBase.readinto"><code class="xref py py-meth docutils literal notranslate"><span class="pre">readinto()</span></code></a> 需要参数内容的写入权限。缓冲区接口使得对象可以选择性地允许或拒绝读写或只读缓冲区的导出。</p>
<p>对于缓冲接口的消费者而言，有两种方式来获取一个目的对象的缓冲。</p>
<ul class="simple">
<li><p>使用正确的参数来调用 <a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyObject_GetBuffer()</span></code></a>  函数</p></li>
<li><p>调用 <a class="reference internal" href="arg.html#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyArg_ParseTuple()</span></code></a> (或其同级对象之一) 并传入 <code class="docutils literal notranslate"><span class="pre">y*</span></code>, <code class="docutils literal notranslate"><span class="pre">w*</span></code> or <code class="docutils literal notranslate"><span class="pre">s*</span></code> <a class="reference internal" href="arg.html#arg-parsing"><span class="std std-ref">格式代码</span></a> 中的一个。</p></li>
</ul>
<p>在这两种情况下，当不再需要缓冲区时必须调用 <a class="reference internal" href="#c.PyBuffer_Release" title="PyBuffer_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBuffer_Release()</span></code></a> 。如果此操作失败，可能会导致各种问题，例如资源泄漏。</p>
<div class="section" id="buffer-structure">
<span id="id1"></span><h2>缓冲区结构<a class="headerlink" href="#buffer-structure" title="永久链接至标题">¶</a></h2>
<p>缓冲区结构(或者简单地称为“buffers”)对于将二进制数据从另一个对象公开给Python程序员非常有用。它们还可以用作零拷贝切片机制。使用它们引用内存块的能力，可以很容易地将任何数据公开给Python程序员。内存可以是C扩展中的一个大的常量数组，也可以是在传递到操作系统库之前用于操作的原始内存块，或者可以用来传递本机内存格式的结构化数据。</p>
<p>与 Python 解释器公开的大多部数据类型不同，缓冲区不是 <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject</span></code></a> 指针而是简单的 C 结构。 这使得它们可以非常简单地创建和复制。 当需要为缓冲区加上泛型包装器时，可以创建一个 <a class="reference internal" href="memoryview.html#memoryview-objects"><span class="std std-ref">内存视图</span></a> 对象。</p>
<p>有关如何编写并导出对象的简短说明，请参阅 <a class="reference internal" href="typeobj.html#buffer-structs"><span class="std std-ref">缓冲区对象结构</span></a>。 要获取缓冲区对象，请参阅 <a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyObject_GetBuffer()</span></code></a>。</p>
<dl class="type">
<dt id="c.Py_buffer">
<code class="sig-name descname">Py_buffer</code><a class="headerlink" href="#c.Py_buffer" title="永久链接至目标">¶</a></dt>
<dd><dl class="member">
<dt id="c.Py_buffer.buf">
void *<code class="sig-name descname">buf</code><a class="headerlink" href="#c.Py_buffer.buf" title="永久链接至目标">¶</a></dt>
<dd><p>指向由缓冲区字段描述的逻辑结构开始的指针。 这可以是导出程序底层物理内存块中的任何位置。 例如，使用负的 <a class="reference internal" href="#c.Py_buffer.strides" title="Py_buffer.strides"><code class="xref c c-member docutils literal notranslate"><span class="pre">strides</span></code></a> 值可能指向内存块的末尾。</p>
<p>对于 <a class="reference internal" href="../glossary.html#term-contiguous"><span class="xref std std-term">contiguous</span></a> ，‘邻接’数组，值指向内存块的开头。</p>
</dd></dl>

<dl class="member">
<dt id="c.Py_buffer.obj">
void *<code class="sig-name descname">obj</code><a class="headerlink" href="#c.Py_buffer.obj" title="永久链接至目标">¶</a></dt>
<dd><p>对导出对象的新引用。 该引用归使用者所有，并由 <a class="reference internal" href="#c.PyBuffer_Release" title="PyBuffer_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBuffer_Release()</span></code></a> 自动递减并设置为 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>。 该字段等于任何标准 C-API 函数的返回值。</p>
<p>作为一种特殊情况，对于由 <a class="reference internal" href="memoryview.html#c.PyMemoryView_FromBuffer" title="PyMemoryView_FromBuffer"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMemoryView_FromBuffer()</span></code></a> 或 <a class="reference internal" href="#c.PyBuffer_FillInfo" title="PyBuffer_FillInfo"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBuffer_FillInfo()</span></code></a> 包装的 <em>temporary</em> 缓冲区，此字段为 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>。 通常，导出对象不得使用此方案。</p>
</dd></dl>

<dl class="member">
<dt id="c.Py_buffer.len">
Py_ssize_t <code class="sig-name descname">len</code><a class="headerlink" href="#c.Py_buffer.len" title="永久链接至目标">¶</a></dt>
<dd><p><code class="docutils literal notranslate"><span class="pre">product(shape)</span> <span class="pre">*</span> <span class="pre">itemsize</span></code>。对于连续数组，这是基础内存块的长度。对于非连续数组，如果逻辑结构复制到连续表示形式，则该长度将具有该长度。</p>
<p>仅当缓冲区是通过保证连续性的请求获取时，才访问 <code class="docutils literal notranslate"><span class="pre">((char</span> <span class="pre">*)buf)[0]</span> <span class="pre">up</span> <span class="pre">to</span> <span class="pre">((char</span> <span class="pre">*)buf)[len-1]</span></code> 时才有效。在大多数情况下，此类请求将为 <a class="reference internal" href="#c.PyBUF_SIMPLE" title="PyBUF_SIMPLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_SIMPLE</span></code></a> 或 <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_WRITABLE</span></code></a>。</p>
</dd></dl>

<dl class="member">
<dt id="c.Py_buffer.readonly">
int <code class="sig-name descname">readonly</code><a class="headerlink" href="#c.Py_buffer.readonly" title="永久链接至目标">¶</a></dt>
<dd><p>缓冲区是否为只读的指示器。此字段由 <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_WRITABLE</span></code></a> 标志控制。</p>
</dd></dl>

<dl class="member">
<dt id="c.Py_buffer.itemsize">
Py_ssize_t <code class="sig-name descname">itemsize</code><a class="headerlink" href="#c.Py_buffer.itemsize" title="永久链接至目标">¶</a></dt>
<dd><p>单个元素的项大小（以字节为单位）。与 <a class="reference internal" href="../library/struct.html#struct.calcsize" title="struct.calcsize"><code class="xref py py-func docutils literal notranslate"><span class="pre">struct.calcsize()</span></code></a> 调用非 <code class="docutils literal notranslate"><span class="pre">NULL</span></code> <a class="reference internal" href="#c.Py_buffer.format" title="Py_buffer.format"><code class="xref c c-member docutils literal notranslate"><span class="pre">format</span></code></a> 的值相同。</p>
<p>重要例外：如果使用者请求的缓冲区没有 <a class="reference internal" href="#c.PyBUF_FORMAT" title="PyBUF_FORMAT"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_FORMAT</span></code></a> 标志，<a class="reference internal" href="#c.Py_buffer.format" title="Py_buffer.format"><code class="xref c c-member docutils literal notranslate"><span class="pre">format</span></code></a> 将设置为 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，但 <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate"><span class="pre">itemsize</span></code></a> 仍具有原始格式的值。</p>
<p>如果 <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate"><span class="pre">shape</span></code></a> 存在，则相等的 <code class="docutils literal notranslate"><span class="pre">product(shape)</span> <span class="pre">*</span> <span class="pre">itemsize</span> <span class="pre">==</span> <span class="pre">len</span></code> 仍然存在，使用者可以使用 <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate"><span class="pre">itemsize</span></code></a> 来导航缓冲区。</p>
<p>如果 <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate"><span class="pre">shape</span></code></a> 是 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，因为结果为 <a class="reference internal" href="#c.PyBUF_SIMPLE" title="PyBUF_SIMPLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_SIMPLE</span></code></a> 或 <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_WRITABLE</span></code></a> 请求，则使用者必须忽略 <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate"><span class="pre">itemsize</span></code></a>，并假设 <code class="docutils literal notranslate"><span class="pre">itemsize</span> <span class="pre">==</span> <span class="pre">1</span></code>。</p>
</dd></dl>

<dl class="member">
<dt id="c.Py_buffer.format">
const char *<code class="sig-name descname">format</code><a class="headerlink" href="#c.Py_buffer.format" title="永久链接至目标">¶</a></dt>
<dd><p>在 <a class="reference internal" href="../library/struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate"><span class="pre">struct</span></code></a> 模块样式语法中 <em>NUL</em> 字符串，描述单个项的内容。如果这是 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，则假定为``&quot;B&quot;`` (无符号字节) 。</p>
<p>此字段由 <a class="reference internal" href="#c.PyBUF_FORMAT" title="PyBUF_FORMAT"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_FORMAT</span></code></a> 标志控制。</p>
</dd></dl>

<dl class="member">
<dt id="c.Py_buffer.ndim">
int <code class="sig-name descname">ndim</code><a class="headerlink" href="#c.Py_buffer.ndim" title="永久链接至目标">¶</a></dt>
<dd><p>The number of dimensions the memory represents as an n-dimensional array.
If it is <code class="docutils literal notranslate"><span class="pre">0</span></code>, <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate"><span class="pre">buf</span></code></a> points to a single item representing
a scalar. In this case, <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate"><span class="pre">shape</span></code></a>, <a class="reference internal" href="#c.Py_buffer.strides" title="Py_buffer.strides"><code class="xref c c-member docutils literal notranslate"><span class="pre">strides</span></code></a>
and <a class="reference internal" href="#c.Py_buffer.suboffsets" title="Py_buffer.suboffsets"><code class="xref c c-member docutils literal notranslate"><span class="pre">suboffsets</span></code></a> MUST be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<p>The macro <code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_MAX_NDIM</span></code> limits the maximum number of dimensions
to 64. Exporters MUST respect this limit, consumers of multi-dimensional
buffers SHOULD be able to handle up to <code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_MAX_NDIM</span></code> dimensions.</p>
</dd></dl>

<dl class="member">
<dt id="c.Py_buffer.shape">
Py_ssize_t *<code class="sig-name descname">shape</code><a class="headerlink" href="#c.Py_buffer.shape" title="永久链接至目标">¶</a></dt>
<dd><p>An array of <code class="xref c c-type docutils literal notranslate"><span class="pre">Py_ssize_t</span></code> of length <a class="reference internal" href="#c.Py_buffer.ndim" title="Py_buffer.ndim"><code class="xref c c-member docutils literal notranslate"><span class="pre">ndim</span></code></a>
indicating the shape of the memory as an n-dimensional array. Note that
<code class="docutils literal notranslate"><span class="pre">shape[0]</span> <span class="pre">*</span> <span class="pre">...</span> <span class="pre">*</span> <span class="pre">shape[ndim-1]</span> <span class="pre">*</span> <span class="pre">itemsize</span></code> MUST be equal to
<a class="reference internal" href="#c.Py_buffer.len" title="Py_buffer.len"><code class="xref c c-member docutils literal notranslate"><span class="pre">len</span></code></a>.</p>
<p>Shape values are restricted to <code class="docutils literal notranslate"><span class="pre">shape[n]</span> <span class="pre">&gt;=</span> <span class="pre">0</span></code>. The case
<code class="docutils literal notranslate"><span class="pre">shape[n]</span> <span class="pre">==</span> <span class="pre">0</span></code> requires special attention. See <a class="reference internal" href="#complex-arrays">complex arrays</a>
for further information.</p>
<p>The shape array is read-only for the consumer.</p>
</dd></dl>

<dl class="member">
<dt id="c.Py_buffer.strides">
Py_ssize_t *<code class="sig-name descname">strides</code><a class="headerlink" href="#c.Py_buffer.strides" title="永久链接至目标">¶</a></dt>
<dd><p>An array of <code class="xref c c-type docutils literal notranslate"><span class="pre">Py_ssize_t</span></code> of length <a class="reference internal" href="#c.Py_buffer.ndim" title="Py_buffer.ndim"><code class="xref c c-member docutils literal notranslate"><span class="pre">ndim</span></code></a>
giving the number of bytes to skip to get to a new element in each
dimension.</p>
<p>Stride values can be any integer. For regular arrays, strides are
usually positive, but a consumer MUST be able to handle the case
<code class="docutils literal notranslate"><span class="pre">strides[n]</span> <span class="pre">&lt;=</span> <span class="pre">0</span></code>. See <a class="reference internal" href="#complex-arrays">complex arrays</a> for further information.</p>
<p>The strides array is read-only for the consumer.</p>
</dd></dl>

<dl class="member">
<dt id="c.Py_buffer.suboffsets">
Py_ssize_t *<code class="sig-name descname">suboffsets</code><a class="headerlink" href="#c.Py_buffer.suboffsets" title="永久链接至目标">¶</a></dt>
<dd><p>An array of <code class="xref c c-type docutils literal notranslate"><span class="pre">Py_ssize_t</span></code> of length <a class="reference internal" href="#c.Py_buffer.ndim" title="Py_buffer.ndim"><code class="xref c c-member docutils literal notranslate"><span class="pre">ndim</span></code></a>.
If <code class="docutils literal notranslate"><span class="pre">suboffsets[n]</span> <span class="pre">&gt;=</span> <span class="pre">0</span></code>, the values stored along the nth dimension are
pointers and the suboffset value dictates how many bytes to add to each
pointer after de-referencing. A suboffset value that is negative
indicates that no de-referencing should occur (striding in a contiguous
memory block).</p>
<p>If all suboffsets are negative (i.e. no de-referencing is needed), then
this field must be <code class="docutils literal notranslate"><span class="pre">NULL</span></code> (the default value).</p>
<p>This type of array representation is used by the Python Imaging Library
(PIL). See <a class="reference internal" href="#complex-arrays">complex arrays</a> for further information how to access elements
of such an array.</p>
<p>The suboffsets array is read-only for the consumer.</p>
</dd></dl>

<dl class="member">
<dt id="c.Py_buffer.internal">
void *<code class="sig-name descname">internal</code><a class="headerlink" href="#c.Py_buffer.internal" title="永久链接至目标">¶</a></dt>
<dd><p>This is for use internally by the exporting object. For example, this
might be re-cast as an integer by the exporter and used to store flags
about whether or not the shape, strides, and suboffsets arrays must be
freed when the buffer is released. The consumer MUST NOT alter this
value.</p>
</dd></dl>

</dd></dl>

</div>
<div class="section" id="buffer-request-types">
<span id="id2"></span><h2>Buffer request types<a class="headerlink" href="#buffer-request-types" title="永久链接至标题">¶</a></h2>
<p>Buffers are usually obtained by sending a buffer request to an exporting
object via <a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyObject_GetBuffer()</span></code></a>. Since the complexity of the logical
structure of the memory can vary drastically, the consumer uses the <em>flags</em>
argument to specify the exact buffer type it can handle.</p>
<p>All <a class="reference internal" href="#c.Py_buffer" title="Py_buffer"><code class="xref c c-data docutils literal notranslate"><span class="pre">Py_buffer</span></code></a> fields are unambiguously defined by the request
type.</p>
<div class="section" id="request-independent-fields">
<h3>request-independent fields<a class="headerlink" href="#request-independent-fields" title="永久链接至标题">¶</a></h3>
<p>The following fields are not influenced by <em>flags</em> and must always be filled in
with the correct values: <a class="reference internal" href="#c.Py_buffer.obj" title="Py_buffer.obj"><code class="xref c c-member docutils literal notranslate"><span class="pre">obj</span></code></a>, <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate"><span class="pre">buf</span></code></a>,
<a class="reference internal" href="#c.Py_buffer.len" title="Py_buffer.len"><code class="xref c c-member docutils literal notranslate"><span class="pre">len</span></code></a>, <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate"><span class="pre">itemsize</span></code></a>, <a class="reference internal" href="#c.Py_buffer.ndim" title="Py_buffer.ndim"><code class="xref c c-member docutils literal notranslate"><span class="pre">ndim</span></code></a>.</p>
</div>
<div class="section" id="readonly-format">
<h3>readonly, format<a class="headerlink" href="#readonly-format" title="永久链接至标题">¶</a></h3>
<blockquote>
<div><dl class="macro">
<dt id="c.PyBUF_WRITABLE">
<code class="sig-name descname">PyBUF_WRITABLE</code><a class="headerlink" href="#c.PyBUF_WRITABLE" title="永久链接至目标">¶</a></dt>
<dd><p>Controls the <a class="reference internal" href="#c.Py_buffer.readonly" title="Py_buffer.readonly"><code class="xref c c-member docutils literal notranslate"><span class="pre">readonly</span></code></a> field. If set, the exporter
MUST provide a writable buffer or else report failure. Otherwise, the
exporter MAY provide either a read-only or writable buffer, but the choice
MUST be consistent for all consumers.</p>
</dd></dl>

<dl class="macro">
<dt id="c.PyBUF_FORMAT">
<code class="sig-name descname">PyBUF_FORMAT</code><a class="headerlink" href="#c.PyBUF_FORMAT" title="永久链接至目标">¶</a></dt>
<dd><p>Controls the <a class="reference internal" href="#c.Py_buffer.format" title="Py_buffer.format"><code class="xref c c-member docutils literal notranslate"><span class="pre">format</span></code></a> field. If set, this field MUST
be filled in correctly. Otherwise, this field MUST be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
</dd></dl>

</div></blockquote>
<p><a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_WRITABLE</span></code></a> can be |'d to any of the flags in the next section.
Since <a class="reference internal" href="#c.PyBUF_SIMPLE" title="PyBUF_SIMPLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_SIMPLE</span></code></a> is defined as 0, <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_WRITABLE</span></code></a>
can be used as a stand-alone flag to request a simple writable buffer.</p>
<p><a class="reference internal" href="#c.PyBUF_FORMAT" title="PyBUF_FORMAT"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_FORMAT</span></code></a> can be |'d to any of the flags except <a class="reference internal" href="#c.PyBUF_SIMPLE" title="PyBUF_SIMPLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_SIMPLE</span></code></a>.
The latter already implies format <code class="docutils literal notranslate"><span class="pre">B</span></code> (unsigned bytes).</p>
</div>
<div class="section" id="shape-strides-suboffsets">
<h3>shape, strides, suboffsets<a class="headerlink" href="#shape-strides-suboffsets" title="永久链接至标题">¶</a></h3>
<p>The flags that control the logical structure of the memory are listed
in decreasing order of complexity. Note that each flag contains all bits
of the flags below it.</p>
<table class="docutils align-default">
<colgroup>
<col style="width: 51%" />
<col style="width: 12%" />
<col style="width: 16%" />
<col style="width: 21%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>请求</p></th>
<th class="head"><p>形状</p></th>
<th class="head"><p>步幅</p></th>
<th class="head"><p>子偏移量</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><dl class="macro">
<dt id="c.PyBUF_INDIRECT">
<code class="sig-name descname">PyBUF_INDIRECT</code><a class="headerlink" href="#c.PyBUF_INDIRECT" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>如果需要的话</p></td>
</tr>
<tr class="row-odd"><td><dl class="macro">
<dt id="c.PyBUF_STRIDES">
<code class="sig-name descname">PyBUF_STRIDES</code><a class="headerlink" href="#c.PyBUF_STRIDES" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>NULL</p></td>
</tr>
<tr class="row-even"><td><dl class="macro">
<dt id="c.PyBUF_ND">
<code class="sig-name descname">PyBUF_ND</code><a class="headerlink" href="#c.PyBUF_ND" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>NULL</p></td>
</tr>
<tr class="row-odd"><td><dl class="macro">
<dt id="c.PyBUF_SIMPLE">
<code class="sig-name descname">PyBUF_SIMPLE</code><a class="headerlink" href="#c.PyBUF_SIMPLE" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>NULL</p></td>
<td><p>NULL</p></td>
<td><p>NULL</p></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="contiguity-requests">
<span id="index-2"></span><h3>连续性的请求<a class="headerlink" href="#contiguity-requests" title="永久链接至标题">¶</a></h3>
<p>C or Fortran <a class="reference internal" href="../glossary.html#term-contiguous"><span class="xref std std-term">contiguity</span></a> can be explicitly requested,
with and without stride information. Without stride information, the buffer
must be C-contiguous.</p>
<table class="docutils align-default">
<colgroup>
<col style="width: 49%" />
<col style="width: 10%" />
<col style="width: 13%" />
<col style="width: 17%" />
<col style="width: 11%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>请求</p></th>
<th class="head"><p>形状</p></th>
<th class="head"><p>步幅</p></th>
<th class="head"><p>子偏移量</p></th>
<th class="head"><p>邻接</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><dl class="macro">
<dt id="c.PyBUF_C_CONTIGUOUS">
<code class="sig-name descname">PyBUF_C_CONTIGUOUS</code><a class="headerlink" href="#c.PyBUF_C_CONTIGUOUS" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>C</p></td>
</tr>
<tr class="row-odd"><td><dl class="macro">
<dt id="c.PyBUF_F_CONTIGUOUS">
<code class="sig-name descname">PyBUF_F_CONTIGUOUS</code><a class="headerlink" href="#c.PyBUF_F_CONTIGUOUS" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>F</p></td>
</tr>
<tr class="row-even"><td><dl class="macro">
<dt id="c.PyBUF_ANY_CONTIGUOUS">
<code class="sig-name descname">PyBUF_ANY_CONTIGUOUS</code><a class="headerlink" href="#c.PyBUF_ANY_CONTIGUOUS" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>C 或 F</p></td>
</tr>
<tr class="row-odd"><td><dl class="macro">
<dt>
<code class="sig-name descname">PyBUF_ND</code></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>NULL</p></td>
<td><p>C</p></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="compound-requests">
<h3>复合请求<a class="headerlink" href="#compound-requests" title="永久链接至标题">¶</a></h3>
<p>所有可能的请求都由上一节中某些标志的组合完全定义。为方便起见，缓冲区协议提供常用的组合作为单个标志。</p>
<p>In the following table <em>U</em> stands for undefined contiguity. The consumer would
have to call <a class="reference internal" href="#c.PyBuffer_IsContiguous" title="PyBuffer_IsContiguous"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBuffer_IsContiguous()</span></code></a> to determine contiguity.</p>
<table class="docutils align-default">
<colgroup>
<col style="width: 36%" />
<col style="width: 8%" />
<col style="width: 11%" />
<col style="width: 14%" />
<col style="width: 9%" />
<col style="width: 12%" />
<col style="width: 9%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>请求</p></th>
<th class="head"><p>形状</p></th>
<th class="head"><p>步幅</p></th>
<th class="head"><p>子偏移量</p></th>
<th class="head"><p>邻接</p></th>
<th class="head"><p>只读</p></th>
<th class="head"><p>格式</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><dl class="macro">
<dt id="c.PyBUF_FULL">
<code class="sig-name descname">PyBUF_FULL</code><a class="headerlink" href="#c.PyBUF_FULL" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>如果需要的话</p></td>
<td><p>U</p></td>
<td><p>0</p></td>
<td><p>是</p></td>
</tr>
<tr class="row-odd"><td><dl class="macro">
<dt id="c.PyBUF_FULL_RO">
<code class="sig-name descname">PyBUF_FULL_RO</code><a class="headerlink" href="#c.PyBUF_FULL_RO" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>如果需要的话</p></td>
<td><p>U</p></td>
<td><p>1 或 0</p></td>
<td><p>是</p></td>
</tr>
<tr class="row-even"><td><dl class="macro">
<dt id="c.PyBUF_RECORDS">
<code class="sig-name descname">PyBUF_RECORDS</code><a class="headerlink" href="#c.PyBUF_RECORDS" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>U</p></td>
<td><p>0</p></td>
<td><p>是</p></td>
</tr>
<tr class="row-odd"><td><dl class="macro">
<dt id="c.PyBUF_RECORDS_RO">
<code class="sig-name descname">PyBUF_RECORDS_RO</code><a class="headerlink" href="#c.PyBUF_RECORDS_RO" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>U</p></td>
<td><p>1 或 0</p></td>
<td><p>是</p></td>
</tr>
<tr class="row-even"><td><dl class="macro">
<dt id="c.PyBUF_STRIDED">
<code class="sig-name descname">PyBUF_STRIDED</code><a class="headerlink" href="#c.PyBUF_STRIDED" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>U</p></td>
<td><p>0</p></td>
<td><p>NULL</p></td>
</tr>
<tr class="row-odd"><td><dl class="macro">
<dt id="c.PyBUF_STRIDED_RO">
<code class="sig-name descname">PyBUF_STRIDED_RO</code><a class="headerlink" href="#c.PyBUF_STRIDED_RO" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>U</p></td>
<td><p>1 或 0</p></td>
<td><p>NULL</p></td>
</tr>
<tr class="row-even"><td><dl class="macro">
<dt id="c.PyBUF_CONTIG">
<code class="sig-name descname">PyBUF_CONTIG</code><a class="headerlink" href="#c.PyBUF_CONTIG" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>NULL</p></td>
<td><p>C</p></td>
<td><p>0</p></td>
<td><p>NULL</p></td>
</tr>
<tr class="row-odd"><td><dl class="macro">
<dt id="c.PyBUF_CONTIG_RO">
<code class="sig-name descname">PyBUF_CONTIG_RO</code><a class="headerlink" href="#c.PyBUF_CONTIG_RO" title="永久链接至目标">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>是</p></td>
<td><p>NULL</p></td>
<td><p>NULL</p></td>
<td><p>C</p></td>
<td><p>1 或 0</p></td>
<td><p>NULL</p></td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="complex-arrays">
<h2>复杂数组<a class="headerlink" href="#complex-arrays" title="永久链接至标题">¶</a></h2>
<div class="section" id="numpy-style-shape-and-strides">
<h3>NumPy-style: shape and strides<a class="headerlink" href="#numpy-style-shape-and-strides" title="永久链接至标题">¶</a></h3>
<p>The logical structure of NumPy-style arrays is defined by <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate"><span class="pre">itemsize</span></code></a>,
<a class="reference internal" href="#c.Py_buffer.ndim" title="Py_buffer.ndim"><code class="xref c c-member docutils literal notranslate"><span class="pre">ndim</span></code></a>, <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate"><span class="pre">shape</span></code></a> and <a class="reference internal" href="#c.Py_buffer.strides" title="Py_buffer.strides"><code class="xref c c-member docutils literal notranslate"><span class="pre">strides</span></code></a>.</p>
<p>If <code class="docutils literal notranslate"><span class="pre">ndim</span> <span class="pre">==</span> <span class="pre">0</span></code>, the memory location pointed to by <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate"><span class="pre">buf</span></code></a> is
interpreted as a scalar of size <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate"><span class="pre">itemsize</span></code></a>. In that case,
both <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate"><span class="pre">shape</span></code></a> and <a class="reference internal" href="#c.Py_buffer.strides" title="Py_buffer.strides"><code class="xref c c-member docutils literal notranslate"><span class="pre">strides</span></code></a> are <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<p>If <a class="reference internal" href="#c.Py_buffer.strides" title="Py_buffer.strides"><code class="xref c c-member docutils literal notranslate"><span class="pre">strides</span></code></a> is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, the array is interpreted as
a standard n-dimensional C-array. Otherwise, the consumer must access an
n-dimensional array as follows:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">ptr</span> <span class="o">=</span> <span class="p">(</span><span class="kt">char</span> <span class="o">*</span><span class="p">)</span><span class="n">buf</span> <span class="o">+</span> <span class="n">indices</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">*</span> <span class="n">strides</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">+</span> <span class="p">...</span> <span class="o">+</span> <span class="n">indices</span><span class="p">[</span><span class="n">n</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span> <span class="o">*</span> <span class="n">strides</span><span class="p">[</span><span class="n">n</span><span class="o">-</span><span class="mi">1</span><span class="p">];</span>
<span class="n">item</span> <span class="o">=</span> <span class="o">*</span><span class="p">((</span><span class="n">typeof</span><span class="p">(</span><span class="n">item</span><span class="p">)</span> <span class="o">*</span><span class="p">)</span><span class="n">ptr</span><span class="p">);</span>
</pre></div>
</div>
<p>As noted above, <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate"><span class="pre">buf</span></code></a> can point to any location within
the actual memory block. An exporter can check the validity of a buffer with
this function:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">verify_structure</span><span class="p">(</span><span class="n">memlen</span><span class="p">,</span> <span class="n">itemsize</span><span class="p">,</span> <span class="n">ndim</span><span class="p">,</span> <span class="n">shape</span><span class="p">,</span> <span class="n">strides</span><span class="p">,</span> <span class="n">offset</span><span class="p">):</span>
    <span class="sd">&quot;&quot;&quot;Verify that the parameters represent a valid array within</span>
<span class="sd">       the bounds of the allocated memory:</span>
<span class="sd">           char *mem: start of the physical memory block</span>
<span class="sd">           memlen: length of the physical memory block</span>
<span class="sd">           offset: (char *)buf - mem</span>
<span class="sd">    &quot;&quot;&quot;</span>
    <span class="k">if</span> <span class="n">offset</span> <span class="o">%</span> <span class="n">itemsize</span><span class="p">:</span>
        <span class="k">return</span> <span class="kc">False</span>
    <span class="k">if</span> <span class="n">offset</span> <span class="o">&lt;</span> <span class="mi">0</span> <span class="ow">or</span> <span class="n">offset</span><span class="o">+</span><span class="n">itemsize</span> <span class="o">&gt;</span> <span class="n">memlen</span><span class="p">:</span>
        <span class="k">return</span> <span class="kc">False</span>
    <span class="k">if</span> <span class="nb">any</span><span class="p">(</span><span class="n">v</span> <span class="o">%</span> <span class="n">itemsize</span> <span class="k">for</span> <span class="n">v</span> <span class="ow">in</span> <span class="n">strides</span><span class="p">):</span>
        <span class="k">return</span> <span class="kc">False</span>

    <span class="k">if</span> <span class="n">ndim</span> <span class="o">&lt;=</span> <span class="mi">0</span><span class="p">:</span>
        <span class="k">return</span> <span class="n">ndim</span> <span class="o">==</span> <span class="mi">0</span> <span class="ow">and</span> <span class="ow">not</span> <span class="n">shape</span> <span class="ow">and</span> <span class="ow">not</span> <span class="n">strides</span>
    <span class="k">if</span> <span class="mi">0</span> <span class="ow">in</span> <span class="n">shape</span><span class="p">:</span>
        <span class="k">return</span> <span class="kc">True</span>

    <span class="n">imin</span> <span class="o">=</span> <span class="nb">sum</span><span class="p">(</span><span class="n">strides</span><span class="p">[</span><span class="n">j</span><span class="p">]</span><span class="o">*</span><span class="p">(</span><span class="n">shape</span><span class="p">[</span><span class="n">j</span><span class="p">]</span><span class="o">-</span><span class="mi">1</span><span class="p">)</span> <span class="k">for</span> <span class="n">j</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">ndim</span><span class="p">)</span>
               <span class="k">if</span> <span class="n">strides</span><span class="p">[</span><span class="n">j</span><span class="p">]</span> <span class="o">&lt;=</span> <span class="mi">0</span><span class="p">)</span>
    <span class="n">imax</span> <span class="o">=</span> <span class="nb">sum</span><span class="p">(</span><span class="n">strides</span><span class="p">[</span><span class="n">j</span><span class="p">]</span><span class="o">*</span><span class="p">(</span><span class="n">shape</span><span class="p">[</span><span class="n">j</span><span class="p">]</span><span class="o">-</span><span class="mi">1</span><span class="p">)</span> <span class="k">for</span> <span class="n">j</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">ndim</span><span class="p">)</span>
               <span class="k">if</span> <span class="n">strides</span><span class="p">[</span><span class="n">j</span><span class="p">]</span> <span class="o">&gt;</span> <span class="mi">0</span><span class="p">)</span>

    <span class="k">return</span> <span class="mi">0</span> <span class="o">&lt;=</span> <span class="n">offset</span><span class="o">+</span><span class="n">imin</span> <span class="ow">and</span> <span class="n">offset</span><span class="o">+</span><span class="n">imax</span><span class="o">+</span><span class="n">itemsize</span> <span class="o">&lt;=</span> <span class="n">memlen</span>
</pre></div>
</div>
</div>
<div class="section" id="pil-style-shape-strides-and-suboffsets">
<h3>PIL-style: shape, strides and suboffsets<a class="headerlink" href="#pil-style-shape-strides-and-suboffsets" title="永久链接至标题">¶</a></h3>
<p>In addition to the regular items, PIL-style arrays can contain pointers
that must be followed in order to get to the next element in a dimension.
For example, the regular three-dimensional C-array <code class="docutils literal notranslate"><span class="pre">char</span> <span class="pre">v[2][2][3]</span></code> can
also be viewed as an array of 2 pointers to 2 two-dimensional arrays:
<code class="docutils literal notranslate"><span class="pre">char</span> <span class="pre">(*v[2])[2][3]</span></code>. In suboffsets representation, those two pointers
can be embedded at the start of <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate"><span class="pre">buf</span></code></a>, pointing
to two <code class="docutils literal notranslate"><span class="pre">char</span> <span class="pre">x[2][3]</span></code> arrays that can be located anywhere in memory.</p>
<p>Here is a function that returns a pointer to the element in an N-D array
pointed to by an N-dimensional index when there are both non-<code class="docutils literal notranslate"><span class="pre">NULL</span></code> strides
and suboffsets:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="kt">void</span> <span class="o">*</span><span class="nf">get_item_pointer</span><span class="p">(</span><span class="kt">int</span> <span class="n">ndim</span><span class="p">,</span> <span class="kt">void</span> <span class="o">*</span><span class="n">buf</span><span class="p">,</span> <span class="n">Py_ssize_t</span> <span class="o">*</span><span class="n">strides</span><span class="p">,</span>
                       <span class="n">Py_ssize_t</span> <span class="o">*</span><span class="n">suboffsets</span><span class="p">,</span> <span class="n">Py_ssize_t</span> <span class="o">*</span><span class="n">indices</span><span class="p">)</span> <span class="p">{</span>
    <span class="kt">char</span> <span class="o">*</span><span class="n">pointer</span> <span class="o">=</span> <span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="p">)</span><span class="n">buf</span><span class="p">;</span>
    <span class="kt">int</span> <span class="n">i</span><span class="p">;</span>
    <span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="n">ndim</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
        <span class="n">pointer</span> <span class="o">+=</span> <span class="n">strides</span><span class="p">[</span><span class="n">i</span><span class="p">]</span> <span class="o">*</span> <span class="n">indices</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>
        <span class="k">if</span> <span class="p">(</span><span class="n">suboffsets</span><span class="p">[</span><span class="n">i</span><span class="p">]</span> <span class="o">&gt;=</span><span class="mi">0</span> <span class="p">)</span> <span class="p">{</span>
            <span class="n">pointer</span> <span class="o">=</span> <span class="o">*</span><span class="p">((</span><span class="kt">char</span><span class="o">**</span><span class="p">)</span><span class="n">pointer</span><span class="p">)</span> <span class="o">+</span> <span class="n">suboffsets</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>
        <span class="p">}</span>
    <span class="p">}</span>
    <span class="k">return</span> <span class="p">(</span><span class="kt">void</span><span class="o">*</span><span class="p">)</span><span class="n">pointer</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="buffer-related-functions">
<h2>Buffer-related functions<a class="headerlink" href="#buffer-related-functions" title="永久链接至标题">¶</a></h2>
<dl class="function">
<dt id="c.PyObject_CheckBuffer">
int <code class="sig-name descname">PyObject_CheckBuffer</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *obj</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyObject_CheckBuffer" title="永久链接至目标">¶</a></dt>
<dd><p>Return <code class="docutils literal notranslate"><span class="pre">1</span></code> if <em>obj</em> supports the buffer interface otherwise <code class="docutils literal notranslate"><span class="pre">0</span></code>.  When <code class="docutils literal notranslate"><span class="pre">1</span></code> is
returned, it doesn't guarantee that <a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyObject_GetBuffer()</span></code></a> will
succeed.  This function always succeeds.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyObject_GetBuffer">
int <code class="sig-name descname">PyObject_GetBuffer</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *exporter</em>, <a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a><em> *view</em>, int<em> flags</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyObject_GetBuffer" title="永久链接至目标">¶</a></dt>
<dd><p>Send a request to <em>exporter</em> to fill in <em>view</em> as specified by  <em>flags</em>.
If the exporter cannot provide a buffer of the exact type, it MUST raise
<code class="xref c c-data docutils literal notranslate"><span class="pre">PyExc_BufferError</span></code>, set <code class="xref c c-member docutils literal notranslate"><span class="pre">view-&gt;obj</span></code> to <code class="docutils literal notranslate"><span class="pre">NULL</span></code> and
return <code class="docutils literal notranslate"><span class="pre">-1</span></code>.</p>
<p>On success, fill in <em>view</em>, set <code class="xref c c-member docutils literal notranslate"><span class="pre">view-&gt;obj</span></code> to a new reference
to <em>exporter</em> and return 0. In the case of chained buffer providers
that redirect requests to a single object, <code class="xref c c-member docutils literal notranslate"><span class="pre">view-&gt;obj</span></code> MAY
refer to this object instead of <em>exporter</em> (See <a class="reference internal" href="typeobj.html#buffer-structs"><span class="std std-ref">Buffer Object Structures</span></a>).</p>
<p>Successful calls to <a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyObject_GetBuffer()</span></code></a> must be paired with calls
to <a class="reference internal" href="#c.PyBuffer_Release" title="PyBuffer_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBuffer_Release()</span></code></a>, similar to <code class="xref c c-func docutils literal notranslate"><span class="pre">malloc()</span></code> and <code class="xref c c-func docutils literal notranslate"><span class="pre">free()</span></code>.
Thus, after the consumer is done with the buffer, <a class="reference internal" href="#c.PyBuffer_Release" title="PyBuffer_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBuffer_Release()</span></code></a>
must be called exactly once.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyBuffer_Release">
void <code class="sig-name descname">PyBuffer_Release</code><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a><em> *view</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_Release" title="永久链接至目标">¶</a></dt>
<dd><p>Release the buffer <em>view</em> and decrement the reference count for
<code class="xref c c-member docutils literal notranslate"><span class="pre">view-&gt;obj</span></code>. This function MUST be called when the buffer
is no longer being used, otherwise reference leaks may occur.</p>
<p>It is an error to call this function on a buffer that was not obtained via
<a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyObject_GetBuffer()</span></code></a>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyBuffer_SizeFromFormat">
Py_ssize_t <code class="sig-name descname">PyBuffer_SizeFromFormat</code><span class="sig-paren">(</span>const char<em> *</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_SizeFromFormat" title="永久链接至目标">¶</a></dt>
<dd><p>Return the implied <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-data docutils literal notranslate"><span class="pre">itemsize</span></code></a> from <a class="reference internal" href="#c.Py_buffer.format" title="Py_buffer.format"><code class="xref c c-data docutils literal notranslate"><span class="pre">format</span></code></a>.
This function is not yet implemented.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyBuffer_IsContiguous">
int <code class="sig-name descname">PyBuffer_IsContiguous</code><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a><em> *view</em>, char<em> order</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_IsContiguous" title="永久链接至目标">¶</a></dt>
<dd><p>Return <code class="docutils literal notranslate"><span class="pre">1</span></code> if the memory defined by the <em>view</em> is C-style (<em>order</em> is
<code class="docutils literal notranslate"><span class="pre">'C'</span></code>) or Fortran-style (<em>order</em> is <code class="docutils literal notranslate"><span class="pre">'F'</span></code>) <a class="reference internal" href="../glossary.html#term-contiguous"><span class="xref std std-term">contiguous</span></a> or either one
(<em>order</em> is <code class="docutils literal notranslate"><span class="pre">'A'</span></code>).  Return <code class="docutils literal notranslate"><span class="pre">0</span></code> otherwise.  This function always succeeds.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyBuffer_GetPointer">
void* <code class="sig-name descname">PyBuffer_GetPointer</code><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a><em> *view</em>, Py_ssize_t<em> *indices</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_GetPointer" title="永久链接至目标">¶</a></dt>
<dd><p>Get the memory area pointed to by the <em>indices</em> inside the given <em>view</em>.
<em>indices</em> must point to an array of <code class="docutils literal notranslate"><span class="pre">view-&gt;ndim</span></code> indices.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyBuffer_FromContiguous">
int <code class="sig-name descname">PyBuffer_FromContiguous</code><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a><em> *view</em>, void<em> *buf</em>, Py_ssize_t<em> len</em>, char<em> fort</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_FromContiguous" title="永久链接至目标">¶</a></dt>
<dd><p>Copy contiguous <em>len</em> bytes from <em>buf</em> to <em>view</em>.
<em>fort</em> can be <code class="docutils literal notranslate"><span class="pre">'C'</span></code> or <code class="docutils literal notranslate"><span class="pre">'F'</span></code> (for C-style or Fortran-style ordering).
<code class="docutils literal notranslate"><span class="pre">0</span></code> is returned on success, <code class="docutils literal notranslate"><span class="pre">-1</span></code> on error.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyBuffer_ToContiguous">
int <code class="sig-name descname">PyBuffer_ToContiguous</code><span class="sig-paren">(</span>void<em> *buf</em>, <a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a><em> *src</em>, Py_ssize_t<em> len</em>, char<em> order</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_ToContiguous" title="永久链接至目标">¶</a></dt>
<dd><p>Copy <em>len</em> bytes from <em>src</em> to its contiguous representation in <em>buf</em>.
<em>order</em> can be <code class="docutils literal notranslate"><span class="pre">'C'</span></code> or <code class="docutils literal notranslate"><span class="pre">'F'</span></code> or <code class="docutils literal notranslate"><span class="pre">'A'</span></code> (for C-style or Fortran-style
ordering or either one). <code class="docutils literal notranslate"><span class="pre">0</span></code> is returned on success, <code class="docutils literal notranslate"><span class="pre">-1</span></code> on error.</p>
<p>This function fails if <em>len</em> != <em>src-&gt;len</em>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyBuffer_FillContiguousStrides">
void <code class="sig-name descname">PyBuffer_FillContiguousStrides</code><span class="sig-paren">(</span>int<em> ndims</em>, Py_ssize_t<em> *shape</em>, Py_ssize_t<em> *strides</em>, int<em> itemsize</em>, char<em> order</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_FillContiguousStrides" title="永久链接至目标">¶</a></dt>
<dd><p>Fill the <em>strides</em> array with byte-strides of a <a class="reference internal" href="../glossary.html#term-contiguous"><span class="xref std std-term">contiguous</span></a> (C-style if
<em>order</em> is <code class="docutils literal notranslate"><span class="pre">'C'</span></code> or Fortran-style if <em>order</em> is <code class="docutils literal notranslate"><span class="pre">'F'</span></code>) array of the
given shape with the given number of bytes per element.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyBuffer_FillInfo">
int <code class="sig-name descname">PyBuffer_FillInfo</code><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a><em> *view</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *exporter</em>, void<em> *buf</em>, Py_ssize_t<em> len</em>, int<em> readonly</em>, int<em> flags</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_FillInfo" title="永久链接至目标">¶</a></dt>
<dd><p>Handle buffer requests for an exporter that wants to expose <em>buf</em> of size <em>len</em>
with writability set according to <em>readonly</em>. <em>buf</em> is interpreted as a sequence
of unsigned bytes.</p>
<p>The <em>flags</em> argument indicates the request type. This function always fills in
<em>view</em> as specified by flags, unless <em>buf</em> has been designated as read-only
and <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_WRITABLE</span></code></a> is set in <em>flags</em>.</p>
<p>On success, set <code class="xref c c-member docutils literal notranslate"><span class="pre">view-&gt;obj</span></code> to a new reference to <em>exporter</em> and
return 0. Otherwise, raise <code class="xref c c-data docutils literal notranslate"><span class="pre">PyExc_BufferError</span></code>, set
<code class="xref c c-member docutils literal notranslate"><span class="pre">view-&gt;obj</span></code> to <code class="docutils literal notranslate"><span class="pre">NULL</span></code> and return <code class="docutils literal notranslate"><span class="pre">-1</span></code>;</p>
<p>如果此函数用作 <a class="reference internal" href="typeobj.html#buffer-structs"><span class="std std-ref">getbufferproc</span></a> 的一部分，则 <em>exporter</em> 必须设置为导出对象，并且必须在未修改的情况下传递 <em>flags</em>。否则，<em>exporter</em> 必须是 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>。</p>
</dd></dl>

</div>
</div>


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  <h3><a href="../contents.html">目录</a></h3>
  <ul>
<li><a class="reference internal" href="#">缓冲协议</a><ul>
<li><a class="reference internal" href="#buffer-structure">缓冲区结构</a></li>
<li><a class="reference internal" href="#buffer-request-types">Buffer request types</a><ul>
<li><a class="reference internal" href="#request-independent-fields">request-independent fields</a></li>
<li><a class="reference internal" href="#readonly-format">readonly, format</a></li>
<li><a class="reference internal" href="#shape-strides-suboffsets">shape, strides, suboffsets</a></li>
<li><a class="reference internal" href="#contiguity-requests">连续性的请求</a></li>
<li><a class="reference internal" href="#compound-requests">复合请求</a></li>
</ul>
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<li><a class="reference internal" href="#complex-arrays">复杂数组</a><ul>
<li><a class="reference internal" href="#numpy-style-shape-and-strides">NumPy-style: shape and strides</a></li>
<li><a class="reference internal" href="#pil-style-shape-strides-and-suboffsets">PIL-style: shape, strides and suboffsets</a></li>
</ul>
</li>
<li><a class="reference internal" href="#buffer-related-functions">Buffer-related functions</a></li>
</ul>
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    <a href="https://www.python.org/psf/donations/">请捐助。</a>
    <br />
    最后更新于 6月 29, 2020.
    <a href="../bugs.html">发现了问题</a>？
    <br />
    使用<a href="http://sphinx.pocoo.org/">Sphinx</a>2.3.1 创建。
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